1. Field of the Invention
The present invention relates to a microphone system to be used for an interface technique of a talker and a personal computer, and more particularly to a microphone system in which a position of a sounder (talker) is input as input data to a personal computer and a signal-to-noise (S/N) ratio of a detecting signal of pronunciation is enhanced so that a sound processing (for example, voice recognition) in a next stage can be improved.
2. Description of the Related Art
Examples of the prior art in which a direction of a sound source is detected by using a plurality of microphones include Japanese Unexamined Patent Publication Nos. HEI 4(1992)-72525, HEI 5(1993)-207117 and HEI 7(1995)-336790.
According to the Japanese Unexamined Patent Publication No. HEI 4(19-72525, a spherical received sound detecting section having an integral structure in which six non-directional microphones are arranged at the space of 90 degrees seen from a center of a sphere on surface thereof is used to detect a received sound pressure level of each microphone and a difference signal of opposite microphones, and to calculate a direction of a sound source based on the received sound pressure level and the difference signal so that the direction of the sound source present in a three-dimensional space can easily be obtained with high precision.
Since only the direction of the sound source is detected by using the six nondirectional microphones, said Publication does not disclose that a S/N ratio is improved to extract an object sound.
According to the Japanese Unexamined Patent Publication No. HEI 5(1993)-207117, a talker's voice, that is, a driver's voice to be input to a mobile phone is received by using at least three microphones for detecting his position, a time difference between voice signals is detected, a position of the talker is detected based on the time difference, and a directional microphone is provided in a direction of the talker so that the influence of noises is reduced to enhance recognition of the talker's voice. In said method, three or more superdirectional microphones are used for extracting an object sound and are provided in a direction of the talker. In general, the superdirectional microphone has a total length of 50 cm or more in order to obtain a high directivity. Furthermore, there is no description on an improvement in the S/N ratio to extract the object sound.
According to the Japanese Unexamined Patent Publication No. HEI 7(1995)-336790, a plurality of microphones are provided to select a microphone in which an output has a maximum value or a generation timing is the earliest so that manual operation of the microphone, an interference of a sound signal and manual operation of mixing can automatically be performed and improved. In said method, a single microphone output is used for extracting a direction of a sound source and an object sound. There is also no description on an improvement in the S/N ratio to extract the object sound.
Therefore, the microphone systems according to the prior arts have problems that a structure is not always small and simple and an object sound in a direction of a sound source cannot be extracted with a high S/N ratio.